AR-3a Midrange Dead?

[Guest leopoldstotch]

I have a pair of AR-3a's and last night the midrange on one of the speakers quit working. I took the pot out cleaned it up and still no midrange so I took a pot out of a pair of AR-2ax's(which have resistors in them) and installed that and to no avail I still have no midrange. I have checked all the wiring on the midrange and everything is fine. Is there a way for me to test the midrange to make absolutely certain that it is dead and that there isn't something else wrong? Thanks.

Bruce

[Carlspeak]

>I have a pair of AR-3a's and last night the midrange on one

>of the speakers quit working. I took the pot out cleaned it up

>and still no midrange so I took a pot out of a pair of

>AR-2ax's(which have resistors in them) and installed that and

>to no avail I still have no midrange. I have checked all the

>wiring on the midrange and everything is fine. Is there a way

>for me to test the midrange to make absolutely certain that

>it is dead and that there isn't something else wrong? Thanks.

>

> Bruce

There 2 ways to test it.

An impedence test across the connector leads should yield a reading in the 3-7 ohms range. If nothing, then it definitely is dead.

Connect a sine wave signal generator across those same leads with it set in the 1000-2000 hz range. If it plays then you know it's good.

If not, I have one I can sell you.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[onplane]

Bruce, it’s possible that the pot is OK and the mid-range is OK, yet you still get NO sound. Reason for this is there are additional components in the mid xover.

Carl is correct about measuring the resistance of the mid, by itself. It’s hard to do in circuit, because of the pot and coils that shunt the mid. If you cut the lead on the pot wiper, however, you can then take a resistance measurement from the front of the speaker.

Your last alternative to test the speaker is to connect it directly to your amp, but with the volume turned full OFF! Then very slooooowly raise the volume to see whether you hear sound. Never give the speaker any significant voltage as it may be shorted and could damage your amp. A very small amount of signal will cause the mid to produce sound. (The safest way to connect a raw speaker to your amp would be via the headphone jack. The headphone circuit has built-in current limiting resistors.)

Hope this helps …

Jerry

[dynaco_dan]

Hi there;

I'm going to jump in here now with my 1 1/2 cent opinion.

If you have the front terminal connection drivers, then proceed.

Connect a pair of alligator test leads up to a 1 1/2 volt battery and touch the two driver solder connections.

The driver will bleep or not with an instant connection.

Polarity is not all that important.

This test will not include any pot, coil or cap.

If your driver is a rear conection, you will need to remove the driver and then do the test.

No need to cut or disconnect anything else.

No more than a 1 1/2 volt battery.

Make certain your amplifier is off.

Hope this shortcut helps.

[Guest leopoldstotch]

Ok thanks for the suggestions gentlemen. I have tested the midrange by connecting my amps speaker leads directly to the mid nd it does indeed work! Now, why won't it play and what should be done to correct this problem? I'm not the most handy person in the world, LOL! Would it be easy to put resistors in? I await your suggestions in trouble shooting this problem. It's now 5:30 a.m. and I'm leaving for work and won't be home until 3:30p.m. Thanks again!

bruce

[Carlspeak]

>Ok thanks for the suggestions gentlemen. I have tested the

>midrange by connecting my amps speaker leads directly to the

>mid nd it does indeed work! Now, why won't it play and what

>should be done to correct this problem? I'm not the most handy

>person in the world, LOL! Would it be easy to put resistors

>in? I await your suggestions in trouble shooting this problem.

>It's now 5:30 a.m. and I'm leaving for work and won't be home

>until 3:30p.m. Thanks again!

> bruce

Your problem then is most likely a bad pot or capacitor. However, very rarely, the the wiring or connections are faulty. If you're not savvy with electronic circuits then I suggest you find someone who is to help diagnose what's causing the short.

If you are, you need to 'follow the juice' so to speak. Using a VOM, start at the positive connector (inside the speaker) and work your way thru the circuit that leads to the midrange. Check for continuity at each step and across each crossover element in the signal path. The capacitor is a bit more tricky. You won't get a continuity reading across it. There, I suggest you hook up your amp directly to the ingoing wire and ground. If no music, then the cap is bad. Another approach to check the cap is connect a jumper cable that bypasses the cap. Again hook up your amp and gently raise the volume.

90% of the time the pot is the problem. It's the weakest link in the signal path on those old AR's.

Remember, it's all about the music

Carl

Carl's Custom Loudspeakers

[dynaco_dan]

Hi there;

You did the test, that should never be done.

You connected the amp to the driver without a cap or coil, in this case, for the mid.

You were tempting fate with that one.

I suggest that no one do that, you could have lost the good driver in the wink of an eye.

If you are not sure what to do, always ask, before you attempt something.

The 1 1/2 volt battery test works, safely.

[onplane]

Bruce,

It’s very good news that the mid still produces sound. It’s probably OK.

The hard part, as Carl, mentioned is now tracing what’s going wrong. Again Carl is correct 90+% of the time the problem is with those blasted pots. Pot wiper corrosion is the major reason for pot failure.

Here is a simple test to see whether the pot is actually the cause of your problem:

1. Cut the wire on the pot going to the mid (I think it’s the green wire – inside the pot it’s attached to the wiper)

2. Now solder that wire to the “top” terminal of the pot (this is the terminal that does NOT have the yellow wire – I think it’s a bare wire going to the coil)

Connect your speakers to your amp using the normal connections on the back. What you have done with this mod is equivalent to setting the pot to “max increase”, but you have totally by passed the wiper inside the pot.

If the mid works when wired like this, we know the problem is with the pot.

If you still have no sound, then it’s time to “jump” components until we can get sound. To do this (leave the above mod in place for this test):

1. Connect your amp to both speakers in the normal fashion

2. Make sure that the volume is fairly LOW (and you can judge that by the “good” speaker)

3. Take a piece of wire about 1 foot long that is stripped bare at both ends

4. Now “jump” the coil that is attached to the “top” of the pot by touching one end of the wire to the terminal on the pot where you just soldered the line going to the mid and touch the other end to other end of the coil. If you get sound, then the coil is open.

5. If no sound, then “jump” the resistor that's connected to this coil.

6. If no sound, then “jump” the cap that connected to this resistor

Bruce, purpose in "jumping" is simply to determine what’s NOT working. You cannot solve your problem long term by jumping the bad component without risking your amp or deteriorating the sound.

Hope this helps…

Regards,

Jerry